Method of manufacturing semiconductor device

ABSTRACT

In a step of doping a silicon-based semiconductor film as a TFT active layer such as channel doping or the like, a protective film is formed by a CVD method as a pretreatment so as to prevent the silicon-based semiconductor film from being contaminated and etched. However, in the case of using the protective film formed by the CVD method, the problems in terms of throughput and production cost (an expensive apparatus is required) have been pointed out. The present invention is intended to solve the above-mentioned problems. Instead of the CVD method, a step of forming a chemical oxide film on a silicon-based semiconductor film is introduced as the pretreatment in the step of doping the silicon-based semiconductor film. Alternatively, a step is introduced in which unsaturated bonds present at the surface of the silicon-based semiconductor film are made to terminate with an element (for instance, oxygen) to be bonded with bonding energy higher than that of Si—H bonds. The above-mentioned pretreatment step can prevent the silicon-based semiconductor film from being etched by hydrogen ions used in the doping step.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/053,572filed Jan. 24, 2002, now U.S. Pat. No. 7,151,017, and which claimspriority to Japanese Patent Application No. 2001-019293, filed on Jan.26, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing asemiconductor device using an ion doping method, and more specificallyto a method of forming a protective film as a pretreatment in an iondoping step. In this specification, the “semiconductor device” denotesany of semiconductor devices in general which has a circuit structurewith a thin film transistor (hereinafter abbreviated as a “TFT”), andsemiconductor display device such as an active matrix type liquidcrystal display device, an organic electro-luminescence (EL) displaydevice, or the like are included in this category.

2. Description of the Related Art

Recently, demands for active matrix type liquid crystal display deviceshave increased rapidly and development of the technique formanufacturing TFTs with a semiconductor film formed on a glass substrateor a quartz substrate has been carried out actively. TFTs manufacturedon an insulating substrate such as a glass substrate or the like in aunit of one million and several hundreds of thousands of pieces have toexhibit predetermined electric characteristics according to the functionof an electric circuit to be formed therewith. There is a parametercalled “Vth” as one of the electric characteristics of a TFT.

The “Vth” denotes a gate voltage measured at the moment when a draincurrent of a TFT starts flowing and is defined as a voltage at which aninversion layer is formed in a channel region. Hence, it can be saidthat the higher the Vth is, the higher the TFT operating voltage is.

Note that, the Vth has a problem in that it fluctuates easily by variousexternal factors including, for instance, contamination impurities in anactive layer, fixed and mobile charges in a gate insulating film, aninterface level at an active layer/gate insulating film interface, andthe difference in work function between a gate electrode and an activelayer. In this case, the contamination impurities in an active layer,the mobile charge in a gate insulating film, and the like can be reducedthrough cleaning in processes. However, the fixed charge, the interfacelevel, and the difference in work function depend on the device materialand thus cannot be modified easily.

The above-mentioned external factors cause the Vth of a TFT to shift tothe plus or minus side to vary. In TFT manufacturing steps, control ofvariable Vth is an important technique, and a channel doping techniquehas been known as a Vth control technique. The “channel doping” is atechnique for controlling Vth by adding a predetermined concentration ofimpurity to an active layer located under a gate insulating film toshift the Vth of a TFT intentionally so that the Vth reaches a desiredlevel. For example, a p-type impurity element is used as a dopant whenthe Vth shifts to the minus side, while an n-type impurity element isused as a dopant when the Vth shifts to the plus side. Thus, the Vth iscontrolled.

For such channel doping, an ion doping method for doping with an n-typeor p-type impurity element is used. The ion doping method is a method ofimplanting an impurity element without implementing mass separation.Since the ion doping method employs no mass separation means, it is easyto achieve an increase in area subjected to processing. Hence, the iondoping method is generally applied to the manufacture of an activematrix type liquid crystal display device. In the ion doping method,B(boron), Ga(gallium), or In(indium) is used as a p-type impurity, andP(phosphorus), As(arsenic), Sb(antimony), or the like is used as ann-type impurity.

When a doping process such as channel doping or the like is carried outdirectly with respect to a silicon-based semiconductor film as an activelayer of a TFT, there is a problem in that the silicon-basedsemiconductor film is etched. Conventionally, as measures for solvingthe problem, a protective film such as a silicon oxide film, a siliconoxynitride film, or the like is deposited by a chemical vapor deposition(CVD) method as a pretreatment in a doping step and then the process ofdoping with impurity ions is conducted from the top of the protectivefilm. However, the measures have the following demerits and thereforeare not preferable.

First, since the CVD method is applied to the mere pretreatment, thetime required for the pretreatment is lengthened and the processing timerequired for the whole step of doping with impurity ions is alsolengthened accordingly. Therefore, with respect to the whole step ofdoping with impurity ions, the above-mentioned measures are notpreferable in terms of throughput since the number of substrates to beprocessed per unit time is reduced. In addition, the above-mentionedmeasures also are not preferable in view of the fact that the cost forthe pretreatment increases since a CVD apparatus such as a plasma CVDapparatus, a low pressure CVD apparatus, or the like is used for thepretreatment and thus the whole production cost increases accordingly.Therefore, an easy low-cost measure for preventing etching has beenrequested as a measure for preventing a silicon-based semiconductor filmfrom being etched.

SUMMARY OF THE INVENTION

The present invention is intended to solve the above-mentioned problemsinherent in the conventional technique. More specifically, the presentinvention is intended to provide a step of doping a silicon-basedsemiconductor film with an easy low-cost pretreatment step as a measurefor preventing the silicon-based semiconductor film from being etched.In other words, the present invention is intended to provide a method ofmanufacturing a semiconductor device including a measure for preventinga silicon-based semiconductor film from being etched by theabove-mentioned pretreatment step.

Experiment on Pretreatment for Channel Doping

Since an active layer of a TFT is formed from a silicon-basedsemiconductor film such as an amorphous silicon film, a polycrystallinesilicon film, a crystalline silicon film formed using a catalyticelement, or the like, it is possible to form a chemical oxide film as anultrathin silicon oxide film by an easy treatment step such as an ozonewater treatment or the like. If the above-mentioned chemical oxide filmcan function as a protective film during the step of ion-doping thesilicon-based semiconductor film, the above-mentioned problems of theconventional art can be solved. Accordingly, the following experimentwas conducted under the experimental conditions indicated in Table 1.

In the specification, the chemical oxide film is a film formed by use ofliquid chemicals having oxidation such as ozone water or a hydrogenperoxide solution. In general, the chemical oxide film is 5 nm thick orless.

First, an amorphous silicon film with a thickness of 53 nm was depositedon each of four glass substrates Nos. 1 to 4 at a deposition temperatureof 300 C by a plasma CVD method. Since a natural oxide film was attachedto each amorphous silicon film, it was removed with dilute hydrofluoricacid. Next, with respect to the two substrates Nos. 2 and 4, the wholesurface of the amorphous silicon film was oxidized with ozone water andthus a chemical oxide film (an ultrathin silicon oxide film) with athickness of 5 nm or less was formed. Afterward, using an ion dopingapparatus, the four substrates Nos. 1 to 4 were subjected to a processof doping with a dose of boron having a range of 1×10¹³ to 1×10¹⁴atoms/cm². The experiment was conducted using a material gas obtained bydiluting diborane (B₂H₆) gas with hydrogen as a material gas of theboron with respect to the cases of dilution ratios of 0.1% and 1.0%.After the ion doping, the thickness of the residue of each amorphoussilicon film was measured. Thus, the state of etching caused during thedoping process was examined.

The results of this experiment are shown in FIG. 1. As can be seen fromFIG. 1, it was observed that the amorphous silicon film was etchedduring the doping process when the chemical oxide film had not beenformed on the surface of the amorphous silicon film by the ozone watertreatment, while the amorphous silicon film was hardly etched when thechemical oxide film had been formed on the surface of the amorphoussilicon film. It was also observed that in the case of using diboranegas with a dilution ratio of 0.1%, the etching of the amorphous siliconfilm was progressed further as compared to the case of using diboranegas with a dilution ratio of 1.0%, in other words, a higher hydrogen ionratio caused heavier etching of the amorphous silicon film. Accordingly,it is considered that the reaction with hydrogen ions participates inthe etching of the amorphous silicon film (see FIG. 1).

The results of this experiment show that the chemical oxide film with athickness of 5 nm or less formed using ozone water can prevent theamorphous silicon film from being etched due to the hydrogen ions duringthe doping process. The method of forming the chemical oxide film is notlimited to the treatment with ozone water. The chemical oxide film canbe formed by a treatment with a hydrogen peroxide solution.Alternatively, an ultrathin silicon oxide film can also be formed byultraviolet (UV) irradiation in an atmosphere containing oxygen althoughit is not a chemical oxide film. It is considered that no matter whichmethod is used for its formation, the amorphous silicon film can beprevented from being etched due to the hydrogen ions.

In this experiment, the discussion was directed to the chemical oxidefilm with a thickness of 5 nm or less. However, it is considered thatetching also can be prevented to some degree by making unsaturated bondspresent at the surface of the amorphous silicon film terminate withoxygen when the hydrogen ion ratio is low in the ion doping apparatus.When being terminated with oxygen, the unsaturated bonds become Si—Obonds and the bonding energy (193.5 kcal/mol) of the Si—O bonds ishigher than that (71.5 kcal/mol) of Si—H bonds. Therefore, even when thehydrogen ions approach the Si—O bonds, the reaction with the hydrogenions is depressed. Thus, it is suggested that the amorphous silicon filmcan be prevented from being etched when the unsaturated bonds present atthe surface of the amorphous silicon film are made to terminate with anelement to be bonded with bonding energy higher than that of the Si—Hbonds.

The above-mentioned bonding energies of the Si—H bonds and the Si—Obonds are cited from the data as to the bond strength of diatomicmolecules (Table 1 0.35) described on page 561 of Applied Physics DataBook (edited by The Japan Society of Applied Physics).

According to the above-mentioned experiment, the following inventionsare led out which are effective in the case of doping with a materialgas producing hydrogen ions. Note that examples of the material gasproducing hydrogen ions include diborane(B₂H₆), phosphine(PH₃),arsine(AsH₃), and those obtained through dilution thereof with hydrogen.Furthermore, when ion implantation is conducted using an ionimplantation apparatus having a mass separation means, it is consideredthat the silicon film is not etched since basically hydrogen ions can beremoved by mass separation.

Invention 1

In the step of ion-doping a silicon-based semiconductor film, a step offorming a chemical oxide film on the surface of the silicon-basedsemiconductor film is introduced as a pretreatment in place of theformation of a protective film by the CVD method.

Invention 2

In the step of ion-doping a silicon-based semiconductor film, a step ofterminating unsaturated bonds present at the surface of thesilicon-based semiconductor film with an element to be bonded withbonding energy higher than that (71.5 kcal/mol) of Si—H bonds(hereinafter simply referred to as an “unsaturated bond terminationstep”) is introduced as a pretreatment in place of the formation of aprotective film by the CVD method.

Method of Manufacturing A Semiconductor Device

In order to solve the above-mentioned problems in the conventional art,the configurations of the present invention are described from theviewpoint of the method of manufacturing a semiconductor device.

According to one aspect of the present invention, a method ofmanufacturing a semiconductor device includes a first step of forming asilicon-based semiconductor film on an insulating substrate and a secondstep of doping the silicon-based semiconductor film with impurity ions,and is characterized in that the second step includes, as apretreatment, the steps of: forming a chemical oxide film on the surfaceof the silicon-based semiconductor film; terminating unsaturated bondspresent at the surface of the silicon-based semiconductor film withoxygen; or terminating the unsaturated bonds present at the surface ofthe silicon-based semiconductor film with an element to be bonded withbonding energy higher than that of Si—H bonds.

According to another aspect of the present invention, a method ofmanufacturing a semiconductor device includes: a first step of forming asilicon-containing amorphous semiconductor film on an insulatingsubstrate; a second step of carrying out channel doping with respect tothe silicon-containing amorphous semiconductor film; a third step ofheat-treating the silicon-containing amorphous semiconductor film toform a silicon-containing polycrystalline semiconductor film; a fourthstep of forming a semiconductor film to serve as an active layer of aTFT through pattern formation of the silicon-containing polycrystallinesemiconductor film; a fifth step of depositing a gate insulating film onthe semiconductor film; a sixth step of forming gate electrodes on thesemiconductor film with the gate insulating film interposedtherebetween; and a seventh step of doping the semiconductor film withimpurity ions with the gate electrodes used as a mask, and ischaracterized in that the second step includes, as a pretreatment, thesteps of: forming a chemical oxide film on the surface of thesilicon-containing amorphous semiconductor film; terminating unsaturatedbonds present at the surface of the silicon-containing amorphoussemiconductor film with oxygen; or terminating the unsaturated bondspresent at the surface of the silicon-containing amorphous semiconductorfilm with an element to be bonded with bonding energy higher than thatof Si—H bonds.

According to still another aspect of the present invention, a method ofmanufacturing a semiconductor device includes: a first step ofdepositing a silicon-containing amorphous semiconductor film on aninsulating substrate and heat-treating it to form a silicon-containingpolycrystalline semiconductor film; a second step of carrying outchannel doping with respect to the silicon-containing polycrystallinesemiconductor film; a third step of forming a semiconductor film toserve as an active layer of a TFT through pattern formation of thesilicon-containing polycrystalline semiconductor film; a fourth step ofdepositing a gate insulating film on the semiconductor film; a fifthstep of forming gate electrodes on the semiconductor film with the gateinsulating film interposed therebetween; and a sixth step of doping thesemiconductor film with impurity ions with the gate electrodes used as amask, and is characterized in that the second step includes, as apretreatment, the steps of: forming a chemical oxide film on the surfaceof the silicon-containing polycrystalline semiconductor film;terminating unsaturated bonds present at the surface of thesilicon-containing polycrystalline semiconductor film with oxygen; orterminating the unsaturated bonds present at the surface of thesilicon-containing polycrystalline semiconductor film with an element tobe bonded with bonding energy higher than that of Si—H bonds.

According to yet another aspect of the present invention, a method ofmanufacturing a semiconductor device includes: a first step ofdepositing a silicon-containing amorphous semiconductor film on aninsulating substrate, adding a catalytic element having an effect ofaccelerating crystallization to the amorphous semiconductor film, andheat-treating it to form a silicon-containing crystalline semiconductorfilm; a second step of carrying out channel doping with respect to thesilicon-containing crystalline semiconductor film; a third step offorming a semiconductor film to serve as an active layer of a TFTthrough pattern formation of the silicon-containing crystallinesemiconductor film; a fourth step of depositing a gate insulating filmon the semiconductor film; a fifth step of forming gate electrodes onthe semiconductor film with the gate insulating film interposedtherebetween; and a sixth step of doping the semiconductor film withimpurity ions with the gate electrodes used as a mask, and ischaracterized in that the second step includes, as a pretreatment thesteps of: forming a chemical oxide film on the surface of thesilicon-containing crystalline semiconductor film; terminatingunsaturated bonds present at the surface of the silicon-containingcrystalline semiconductor film with oxygen; or terminating theunsaturated bonds present at the surface of the silicon-containingcrystalline semiconductor film with an element to be bonded with bondingenergy higher than that of Si—H bonds.

According to another aspect of the present invention, a method ofmanufacturing a semiconductor device includes: a first step ofdepositing a silicon-containing amorphous semiconductor film on aninsulating substrate; a second step of carrying out channel doping withrespect to the silicon-containing amorphous semiconductor film; a thirdstep of adding a catalytic element having an effect of acceleratingcrystallization to the silicon-containing amorphous semiconductor filmand heat-treating it to form a silicon-containing crystallinesemiconductor film; a fourth step of forming a semiconductor film toserve as an active layer of a TFT through pattern formation of thesilicon-containing crystalline semiconductor film; a fifth step ofdepositing a gate insulating film on the semiconductor film; a sixthstep of forming gate electrodes on the semiconductor film with the gateinsulating film interposed therebetween; and a seventh step of dopingthe semiconductor film with impurity ions with the gate electrodes usedas a mask, and is characterized in that the second step includes, as apretreatment, the steps of: forming a chemical oxide film on the surfaceof the silicon-containing amorphous semiconductor film; terminatingunsaturated bonds present at the surface of the silicon-containingamorphous semiconductor film with oxygen; or terminating the unsaturatedbonds present at the surface of the silicon-containing amorphoussemiconductor film with an element to be bonded with bonding energyhigher than that of Si—H bonds.

In the above-mentioned aspects of the present invention, thesilicon-based semiconductor film is not limited as long as it is asemiconductor film containing silicon. The silicon-based semiconductorfilm may be, for example, a silicon-containing amorphous semiconductorfilm, a silicon-containing polycrystalline semiconductor film that isobtained by heat-treating a silicon-containing amorphous semiconductorfilm, or a silicon-containing crystalline semiconductor film that isobtained by adding a catalytic element having an effect of acceleratingcrystallization to a silicon-containing amorphous semiconductor film andheat-treating it. In this specification, the technical terms of asilicon-containing amorphous semiconductor film, a silicon-containingpolycrystalline semiconductor film, and a silicon-containing crystallinesemiconductor film are distinguished from one another in their use.Hence, their definitions are made clear as follows. The“silicon-containing amorphous semiconductor film” denotes asilicon-containing amorphous film that is provided with semiconductorproperties by being crystallized. The term of the silicon-containingamorphous semiconductor film, of course, covers amorphous silicon filmsand further all the silicon-containing amorphous semiconductor films.For example, the term also covers amorphous films formed of a compoundof silicon and germanium expressed by a formula of Si_(x)Ge_(1-x)(0<X<1). The “silicon-containing crystalline semiconductor film” denotesa crystalline semiconductor film that is obtained using a catalyticelement having an effect of accelerating crystallization. Thesilicon-containing crystalline semiconductor film is characterized byhaving crystal grains orientated in substantially the same direction,having higher field-effect mobility, and the like as compared to anordinary polycrystalline semiconductor film. Hence, thesilicon-containing crystalline semiconductor is described intentionallyin distinction from the polycrystalline semiconductor film.

Here, the description is directed to the catalytic element having aneffect of accelerating crystallization. The catalytic element is addedto a silicon-containing amorphous semiconductor film in order toaccelerate its crystallization. A metallic element such as Ni(nickel) orthe like is used as the catalytic element. Besides the Ni element,typical metallic elements used as the catalytic element includeFe(iron), Co(cobalt), Ru(ruthenium), Rh(rhodium), Pd(palladium),Os(osmium), Ir(iridium), Pt(platinum), Cu(copper), Au(gold), and thelike. As the catalytic element, usually one selected element is used,but a combination of two elements or more may be used. According to theexperiments implemented by the present inventors et al., it has beenproved that the Ni element is the most preferable catalytic element.

Furthermore, in the above-mentioned aspects of the present invention,examples of the impurity ions include n-type impurities represented by aP(phosphorus) element and an As(arsenic) element and p-type impuritiesrepresented by a B(boron) element. When using the phosphorous element,the As element, and the boron element, an ion source obtained bydiluting phosphine (PH₃) with hydrogen, an ion source obtained bydiluting arsine (AsH₃) with hydrogen, and an ion source obtained bydiluting diborane (B₂H₆) with hydrogen are used, respectively. Since allthe ion sources are obtained through dilution with hydrogen, hydrogenions are produced in doping. It is considered that when a silicon-basedsemiconductor film is doped with such impurity ions, the hydrogen ionsact as an etchant for the silicon-based semiconductor film.

In the above-mentioned aspects of the present invention, a typicalexample of the chemical oxide film formed on the surface of thesilicon-based semiconductor film is a silicon oxide film with athickness of 5 nm or less obtained by a treatment with ozone water, butthe chemical oxide film may be formed by a treatment with a hydrogenperoxide solution. Alternatively, an ultrathin silicon oxide film havingan effect similar to that of the chemical oxide film can also be formedby ultraviolet (UV) irradiation in an atmosphere containing oxygenalthough it is not an exact chemical oxide film. Furthermore, in placeof the formation of the chemical oxide film, it is also considered toterminate unsaturated bonds present at the surface of the silicon-basedsemiconductor film with oxygen or with an element to be bonded withbonding energy higher than that of Si—H bonds.

According to the present invention with the configurations as describedabove, since a chemical oxide film formed by a simple method is used asa protective film for the silicon-based semiconductor film when thesilicon-based semiconductor film is doped with impurity ions, thepresent invention is effective in improving throughput of the whole iondoping step. In addition, since an expensive plasma CVD apparatus or lowpressure CVD apparatus is no longer necessary for the pretreatment inthe ion doping step, the present invention is effective in reducingproduction cost. In the case where unsaturated bonds present at thesurface of the silicon-based semiconductor film are made to terminatewith an element to be bonded with bonding energy higher than that ofSi—H bonds, for example, with oxygen in place of the formation of thechemical oxide film, this termination step is considered to have aneffect similar to that of the chemical oxide film since it is easierthan the CVD step.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 shows experimental data indicating dependence of the thickness ofan amorphous silicon residual film on a dose;

FIGS. 2A to 2E are cross-sectional views showing TFT manufacturingsteps;

FIGS. 3A to 3D are cross-sectional views showing TFT manufacturingsteps;

FIGS. 4A to 4E are cross-sectional views showing TFT manufacturingsteps;

FIGS. 5A and 5B show data as to I_(D)−V_(G) (current-voltage)characteristics of an n-channel type TFT;

FIGS. 6A and 6B are cross-sectional views showing steps of manufacturingan active matrix type liquid crystal display device;

FIGS. 7A and 7B are cross-sectional views showing steps of manufacturingthe active matrix type liquid crystal display device;

FIGS. 8A and 8B are cross-sectional views showing steps of manufacturingthe active matrix type liquid crystal display device;

FIGS. 9A and 9B are cross-sectional views showing steps of manufacturingthe active matrix type liquid crystal display device;

FIGS. 10A and 10B are cross-sectional views showing steps ofmanufacturing the active matrix type liquid crystal display device;

FIGS. 11A to 11F are schematic drawings showing devices as examples ofelectronic equipment with a semiconductor display device installedtherein;

FIGS. 12A to 12D are schematic drawings showing devices as examples ofelectronic equipment with a semiconductor display device installedtherein; and

FIGS. 13A to 13C are schematic drawings showing devices as examples ofelectronic equipment with a semiconductor display device installedtherein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment Mode 1

In the present embodiment mode, as an example of a method ofmanufacturing TFTs in which channel doping is conducted with respect toa silicon-based semiconductor film with a crystal structure, a method ofmanufacturing TFTs in which channel doping is conducted with respect toa crystalline silicon film crystallized using a catalytic element isdescribed concretely with reference to FIGS. 2A to 3D. Note that thechannel doping is conducted with respect to an n-channel type TFT alone.

First, a base film 102 made of a silicon oxynitride film with athickness of 100 nm is deposited on a glass substrate 101 by the plasmaCVD method. Subsequently, an amorphous silicon film 103 with a thicknessof 15 to 70 nm, more preferably a thickness of 30 to 60 nm is depositedthereon. In the present embodiment mode, the amorphous silicon film 103with a thickness of 50 nm was deposited by the plasma CVD method. Indepositing the amorphous silicon film 103, a natural oxide film (notshown) is attached to the surface of the amorphous silicon film 103 dueto the effect of oxygen in the air. Therefore, washing is implemented bya treatment with dilute hydrofluoric acid. Afterward, a chemical oxidefilm 104 made from an ultrathin silicon oxide film is formed on thesurface of the amorphous silicon film 103 by an ozone water treatmentconducted for a predetermined time. This chemical oxide film 104 isformed for the purpose of improving wettability with respect to a Niaqueous solution as a solution including a catalytic element(hereinafter referred to as a “catalytic element solution”) to beapplied later by a spin coating method. Note that in the presentembodiment mode, the amorphous silicon film 103 was deposited, butbesides the amorphous silicon film 103, it is also possible to use asilicon-containing amorphous semiconductor film, for example, anamorphous semiconductor film made of a compound of silicon and germaniumexpressed by a formula of Si_(x)Ge_(1-x) (0<X<1). Furthermore, thechemical oxide film 104 was formed by the ozone water treatment but maybe formed by a treatment with a hydrogen peroxide solution (see FIG.2A).

Next, the Ni aqueous solution as a catalytic element solution is appliedto the whole surface of the amorphous silicon film 103 (strictlyspeaking, the chemical oxide film 104) by the spin coating method.Preferable Ni concentration of the Ni aqueous solution is in the rangeof 0.1 to 50 ppm by weight, more preferably about 1 to 30 ppm by weight.In the present embodiment mode, a Ni aqueous solution with a Niconcentration of 10 ppm by weight was applied by the spin coatingmethod. In the spin coating, the substrate is rotated and thus an excessof the Ni aqueous solution is blown off to be removed. Thus, anultrathin Ni-containing film 105 is formed over the whole surface of theamorphous silicon film 103 (strictly speaking, the chemical oxide film104) (see FIG. 2B).

Next, the amorphous silicon film 103 is heat-treated in a nitrogenatmosphere using a special-purpose heat treating furnace. Due to theeffect of the catalytic element that accelerates crystallization,crystallization is achieved by the heat treatment that is carried out ina temperature range of 450 to 750 C. However, this heat treatment has ageneral characteristic that a treatment time is lengthened when the heattreatment temperature is low, thereby decreasing production efficiency.In addition, in the heat treatment at 600 C or higher, there arises aproblem in heat resistance of the glass substrate used as the substrate.Hence, when the glass substrate is used, a suitable temperature to beemployed in the above-mentioned heat treatment step is in the range of450 C to 600 C. Furthermore, suitable heat treatment conditions in anactual heat treatment vary depending on the method of depositing theamorphous silicon film 103. It has been proved that, for instance, whenthe amorphous silicon film 103 is deposited by a low pressure CVDmethod, it is suitable to carry out the heat treatment at 600 C forabout 12 hours, and when the amorphous silicon film 103 is deposited bythe plasma CVD method, it is sufficient to carry out the heat treatmentat 550 C for about 4 hours. In the present embodiment mode, since theamorphous silicon film 103 with a thickness of 50 nm was deposited bythe plasma CVD method, a heat treatment was carried out at 550 C for 4hours to form a crystalline silicon film 106. As described above, thecrystal growth method in which the Ni aqueous solution is applied to thewhole surface of the amorphous silicon film 103, and then heat-treatmentis conducted is named a longitudinal growth method by the presentinventors et al. since the crystal growth progresses in the longitudinaldirection from the surface of the amorphous silicon film 103 (in thedirection perpendicular to the substrate surface) with the Ni elementapplied thereto (see FIG. 2B).

Next, in order to improve the crystallinity of the crystalline siliconfilm 106 thus obtained, laser irradiation is conducted with respect tothe crystalline silicon film 106. When only being heat-treated by usingan electrothermal furnace, the crystalline silicon film 106 is in animperfectly crystallized state and includes amorphous componentsirregularly remaining therein. In this embodiment mode, for the purposeof improving the imperfect crystallization, a pulse oscillation type KrFexcimer laser (with a wavelength of 248 nm) is used for the laserirradiation with respect to the crystalline silicon film 106. Since thisexcimer laser emits ultraviolet light, instantaneous melting andsolidification are repeated in the region subjected to the laserirradiation. Hence, in the region subjected to the laser irradiation, akind of non-equilibrium state is realized, which results in a statewhere the Ni element can move very easily. It is also possible to omitthis laser irradiation step. Besides the effect of improvingcrystallinity, however, the laser irradiation step also provides aneffect of improving the efficiency of the later gettering step. Hence,it is preferable that the laser irradiation step be not omitted (seeFIG. 2B).

Next, since a contamination film such as the Ni-containing film 105 orthe like is attached to the surface of the crystalline silicon film 106thus obtained, it is washed with dilute hydrofluoric acid, therebycleaning the surface of the crystalline silicon film 106. Afterward, asa pretreatment for channel doping, an ozone water treatment is carriedout for a predetermined time to form a chemical oxide film 107 made ofan ultrathin silicon oxide film with a thickness of 5 nm or less on thesurface of the crystalline silicon film 106. In this embodiment mode,the chemical oxide film 107 is formed by the ozone water treatment butmay be formed by a treatment with a hydrogen peroxide solution. Anultrathin silicon oxide film having a similar effect to that of thechemical oxide film can also be formed by ultraviolet (UV) irradiationin an atmosphere containing oxygen although it is not an exact chemicaloxide film (FIG. 2C).

When the hydrogen ion ratio is low in an ion doping apparatus used inthe channel doping step, it is also considered as the pretreatment forchannel doping that unsaturated bonds present at the surface of thecrystalline silicon film 106 are made to terminate with an element to bebonded with bonding energy higher than that (71.5 kcal/mol) of Si—Hbonds such as oxygen or the like.

Next, a resist pattern 108 to serve as a mask for channel doping isformed with using the region corresponding to an n-channel type TFT ofthe crystalline silicon film 106 as its opening region. Afterward, usingthe ion doping apparatus, the region corresponding to the n-channel typeTFT of the crystalline silicon film 106 is doped with a boron element asa p-type impurity with the resist pattern 108 used as a mask, and thuschannel doping is implemented. In the channel doping, an ion source isused that is obtained through dilution of diborane (B₂H₆) gas withhydrogen. Generally, the channel doping is carried out under the dopingconditions including a diborane dilution ratio of 0.01 to 1.0%, anaccelerating voltage of 1 to 50 kV, an ion current of 10 to 500 nA, anda dose of 1×10¹¹ to 1×10¹⁴ atoms/cm². In the present embodiment mode,the doping process was carried out under the channel doping conditionsincluding a diborane dilution ratio of 0.1%, an accelerating voltage of15 kV, an ion current of 50 nA, and a dose of 4×10¹³ atoms/cm² (see FIG.2C).

Next, the resist pattern 108 that has served as a mask for channeldoping is removed. Afterward, pattern formation of the crystallinesilicon film 106 is carried out by ordinary photolithography and dryetching to form a semiconductor film 109 n corresponding to then-channel type TFT and a semiconductor film 109 p corresponding to ap-channel type TFT. Here, a natural oxide film (or the chemical oxidefilm 107 formed by the pretreatment for channel doping) has been formedon each surface of the semiconductor films 109 n and 109 p. Hence, it isremoved by a treatment with dilute hydrofluoric acid. In this manner,the surfaces of the semiconductor films 109 n and 109 p made of thecrystalline silicon film 106 are cleaned and then a gate insulating film110 made of a silicon oxide film with a thickness of 100 nm is formed bythe plasma CVD method or the low pressure CVD method (see FIG. 2D).

Next, an conductive film (with a thickness of 400 nm) as a gateelectrode material is deposited by a sputtering method or a CVD methodand is subjected to pattern formation by the ordinary photolithographyand dry etching. Thus, a gate electrode 111 n corresponding to then-channel type TFT and a gate electrode 111 p corresponding to thep-channel type TFT are formed. As a gate electrode material used here, aheat resistant material is preferable that can withstand the heattreatment temperature (about 550 to 650 C) for gettering as a later stepthat also serves for activating the impurity ions with which thesemiconductor films 109 n and 109 p are doped. Examples of the heatresistant material include high melting metals such as Ta(tantalum),Mo(molybdenum), Ti(titanium), W(tungsten), Cr(chromium), and the like,metal silicide as a compound of a high melting metal and silicon,polycrystalline silicon having n-type or p-type conductivity, and thelike. In the present embodiment mode, a W metal film with a thickness of400 nm was applied (see FIG. 2E).

Next, using the ion doping apparatus, doping with a phosphorous elementas an n-type impurity is conducted with the gate electrodes 111 n and111 p used as a mask. This ion doping process is carried out under theconditions including an accelerating voltage of 10 to 100 kV and a doseof 1×10¹⁴ to 1×10¹⁶ atoms/cm². In the present embodiment mode, thedoping process was carried out under the conditions including anaccelerating voltage of 80 kV and a dose of 1.7×10¹⁵ atoms/cm². By thision doping process, high-concentration impurity regions (n⁺ regions) 113n having an n type conductivity type to function as source and drainregions and a substantially intrinsic region 112 n to function as achannel region are formed in the semiconductor film 109 n correspondingto the n-channel type TFT. Additionally, in the semiconductor film 109 pcorresponding to the p-channel type TFT are formed high-concentrationimpurity regions (n⁺ regions) 113 p having an n type conductivity typeand a substantially intrinsic region 112 p to function as a channelregion (see FIG. 2E).

Next, a resist pattern 114 is formed with using the whole region of thesemiconductor film 109 p corresponding to the p-channel type TFT as itsopening region. Afterward, using the ion doping apparatus, doping with aboron element as a p-type impurity is conducted with the resist pattern114 and the gate electrode 111 p corresponding to the p-channel type TFTused as a mask. This ion doping process is carried out under theconditions including an accelerating voltage of 10 to 100 kV and a doseof 2×10¹⁴ to 5×10¹⁶ atoms/cm². In the present embodiment mode, thedoping process was carried out under the conditions including anaccelerating voltage of 60 kV and a dose of 2.5×10¹⁵ atoms/cm². This iondoping process causes reversal of the conductivity type of the n-typehigh-concentration impurity regions 113 p corresponding to the p-channeltype TFT to form high-concentration impurity regions (p⁺ regions) 115 phaving a p type conductivity type to function as source and drainregions (see FIG. 3A).

Next, after the resist pattern 114 is removed, a first interlayerinsulating film 116 made from an inorganic film with a thickness of 100to 300 nm is deposited. In this embodiment mode, the first interlayerinsulating film 116 is deposited which is formed from a siliconoxynitride film with a thickness of 150 nm by the plasma CVD method.Afterward, for the purpose of thermal activation of the impurityelements (the n-type and p-type impurities) with which the semiconductorfilms 109 n and 109 p have been doped, a heat treatment is conducted at600 C for 12 hours using an electrothermal furnace. This heat treatmentis carried out for the thermal activation process of the impurityelements but also for gettering process of an unwanted catalytic element(Ni element) contained in the substantially intrinsic regions 112 n and112 p to function as channel regions. The TFTs having the crystallinesilicon film manufactured by this method have high field-effect mobilityand excellent electric characteristics such as a reduced off-statecurrent or the like since the unwanted catalytic element (Ni element) inthe channel regions is gettered. Afterward, in order to terminateunsaturated bonds present at the surfaces of the semiconductor films 109n and 109 p, a hydrogen treatment is conducted in a 3%hydrogen-containing nitrogen atmosphere at 410 C for one hour (see FIG.3B).

Next, a second interlayer insulating film 117 made of a transparentorganic film with a thickness of 1 to 3 μm is formed on the firstinterlayer insulating film 116. In this embodiment mode, a secondinterlayer insulating film 117 is formed from an acrylic resin film witha thickness of 1.6 μm. Afterward, by the ordinary photolithography anddry etching, contact holes 118 are formed in the gate insulating film110 present under the first interlayer film 116 as well as the secondinterlayer insulating film 117 and the first interlayer insulating film116 (FIG.3C).

Next, a metal film with a thickness of 200 to 800 nm having conductivityis deposited. In the present embodiment mode, a laminated film composedof a Ti film with a thickness of 50 nm and an Al—Ti alloy film with athickness of 500 nm is deposited by the sputtering method. Afterward,the ordinary photolithography and dry etching are carried out to formmetal wirings 119. The respective metal wirings 119 are connected to thesource and drain regions 113 n corresponding to the n-channel type TFTand to the source and drain regions 115 p corresponding to the p-channeltype TFT through the contact holes 118 (see FIG. 3D).

As described above, the TFTs can be manufactured through application ofthe channel doping pretreatment step of forming a chemical oxide filmand channel doping with respect to the crystalline silicon film formedusing a catalytic element. The step of forming the chemical oxide filmis applied as the pretreatment for channel doping because it provides aneffect of preventing the crystalline silicon film from being etchedduring the channel doping. However, when unsaturated bonds present atthe crystalline silicon film surface are made to terminate with anelement to be bonded with bonding energy higher than that (71.5kcal/mol) of the Si—H bonds such as oxygen, an etching protective effectsimilar to that provided by the formation of a chemical oxide film canbe expected. In this embodiment mode, the channel doping pretreatmentstep of forming a chemical oxide film and channel doping are applied tothe formation of the crystalline silicon film using the catalyticelement but of course, can be applied to the formation of an ordinarypolycrystalline silicon film crystallized by a simple heat treatmentalone (without using the catalytic element).

Embodiment Mode 2

In the present embodiment mode, an example of a TFT manufacturing methodin which channel doping is carried out with respect to an amorphoussilicon film is described concretely with reference to FIGS. 4A to 5B.Here, the channel doping is carried out only with respect to ann-channel type TFT. In addition, the description with respect to thestep of crystallizing the amorphous silicon film after the channeldoping is directed to the case where crystallization is conducted usinga catalytic element. The steps carried out after the deposition of agate insulating film (including the steps shown in FIGS. 3A to 3D inEmbodiment mode 1) are basically identical to those in Embodiment mode 1and therefore their description is omitted here.

First, a base film 202 made of a silicon oxynitride film with athickness of 100 nm is deposited on a glass substrate 201 by the plasmaCVD method. Subsequently, an amorphous silicon film 203 with a thicknessof 15 to 70 nm, more preferably a thickness of 30 to 60 nm is depositedthereon. In the present embodiment mode, the amorphous silicon film 203with a thickness of 50 nm was deposited by the plasma CVD method. Indepositing the amorphous silicon film 203, since a natural oxide film(not shown) is attached to the surface of the amorphous silicon film 203due to the effect of oxygen in the air. Note that in the presentembodiment mode, the amorphous silicon film 203 was deposited, butbesides the amorphous silicon film 203, it is also possible to apply asilicon-containing amorphous semiconductor film, for example, anamorphous semiconductor film made of a compound of silicon and germaniumexpressed by a formula of Si_(x)Ge_(1-x) (0<X<1) (see FIG. 4A).

Next, the natural oxide film (not shown) attached to the surface of theamorphous silicon film 203 is washed with dilute hydrofluoric acid,thereby increasing the surface of the amorphous silicon film 203.Afterward, as a pretreatment for channel doping, a chemical oxide film204 made of an ultrathin silicon oxide film with a thickness of 5 nm orless is formed on the surface of the amorphous silicon film 203 by anozone water treatment carried out for a predetermined time. Note that inthis embodiment mode, the chemical oxide film 204 is formed by the ozonewater treatment but may be formed by a treatment using a hydrogenperoxide solution. An ultrathin silicon oxide film having a similareffect to that of the chemical oxide film also can be formed byultraviolet (UV) irradiation in an atmosphere containing oxygen althoughit is not an exact chemical oxide film (FIG. 4B).

When the hydrogen ion ratio is low in an ion doping apparatus used inthe channel doping step, it is also considered as the pretreatment forchannel doping that unsaturated bonds present at the surface of theamorphous silicon film 203 are made to terminate with an element to bebonded with bonding energy higher than that (71.5 kcal/mol) of Si—Hbonds such as oxygen.

Next, a resist pattern 205 to serve as a mask for channel doping isformed with using the region corresponding to the n-channel type TFT ofthe amorphous silicon film 203 as its opening region. Afterward, usingthe ion doping apparatus, the region corresponding to the n-channel typeTFT of the amorphous silicon film 203 is doped with a boron element as ap-type impurity with the resist pattern 205 used as a mask, and thuschannel doping is implemented. In the channel doping, an ion sourceobtained through dilution of diborane (B₂H₆) gas with hydrogen is used.Generally, the channel doping is carried out under the doping conditionsincluding a diborane dilution ratio of 0.01 to 1.0%, an acceleratingvoltage of 1 to 50 kV, an ion current of 10 to 500 nA, and a dose of1×10¹¹ to 1×10¹⁴ atoms/cm². In the present embodiment mode, the dopingprocess was carried out under the channel doping conditions including adiborane dilution ratio of 0.1%, an accelerating voltage of 15 kV, anion current of 50 nA, and a dose of 4×10¹³ atoms/cm² (see FIG. 4B).

Next, the resist pattern 205 that has served as a mask for channeldoping is removed. Afterward, washing is carried out by a treatmentusing dilute hydrofluoric acid to clean the surface of the amorphoussilicon film 203. Afterward, a chemical oxide film 206 made of anultrathin silicon oxide film is formed on the surface of the amorphoussilicon film 203 by an ozone water treatment carried out for apredetermined time. This chemical oxide film 206 is formed for thepurpose of improving wettability with respect to a Ni aqueous solutionas a catalytic element solution to be applied later by a spin coatingmethod. Note that in the present embodiment mode, the chemical oxidefilm 206 is formed by the ozone water treatment but may be formed by atreatment using a hydrogen peroxide solution (see FIG. 4C).

Next, the Ni aqueous solution as a catalytic element solution is appliedto the whole surface of the amorphous silicon film 203 (strictlyspeaking, the chemical oxide film 206) by the spin coating method.Preferable Ni concentration of the Ni aqueous solution is in the rangeof 0.1 to 50 ppm by weight, more preferably about 1 to 30 ppm by weight.In the present embodiment mode, a Ni aqueous solution with a Niconcentration of 10 ppm by weight was applied by the spin coatingmethod. In the spin coating, the substrate is rotated and an excess ofthe Ni aqueous solution is blown off to be removed, and thus anultrathin Ni-containing film 207 is formed over the whole surface of theamorphous silicon film 203 (strictly speaking, the chemical oxide film206) (see FIG. 4C).

Next, the amorphous silicon film 203 is heat-treated in a nitrogenatmosphere using a special-purpose heat treating furnace. In thisembodiment mode, since the amorphous silicon film 203 with a thicknessof 50 nm is deposited by the plasma CVD method as in Embodiment mode 1,a heat treatment is conducted at 550 C for four hours to form acrystalline silicon film 208 by the longitudinal growth method.Afterward, in order to improve the crystallinity of the crystallinesilicon film 208 thus obtained, laser irradiation is carried out withrespect to the crystalline silicon film 208. By this laser irradiation,the crystallinity of the crystalline silicon film 208 is improvedconsiderably. In this embodiment mode, a pulse oscillation type KrFexcimer laser (with a wavelength of 248 nm) is applied. This eximerlaser has not only an effect of improving the crystallinity of thecrystalline silicon film 208 but also an effect of improving theefficiency of gettering by a gettering source since the Ni element isbrought into a state where the Ni element can move very easily (see FIG.4C).

Next, pattern formation of the crystalline silicon film 208 is conductedby ordinary photolithography and dry etching to form a semiconductorfilm 209 n corresponding to the n-channel type TFT and a semiconductorfilm 209 p corresponding to a p-channel type TFT. Afterward, washing iscarried out by a treatment using dilute hydrofluoric acid to clean thesurfaces of the semiconductor films 209 n and 209 p. After the cleaningof the surfaces of the semiconductor films 209 n and 209 p, a gateinsulating film 210 made of a silicon oxide film with a thickness of 100nm is deposited by the plasma CVD method or the low pressure CVD method.Note that the TFT manufacturing steps carried out after this step areidentical to those in Embodiment mode 1 and therefore their descriptionis omitted (FIG. 4D).

Evaluation of Electric Characteristics of TFT

In accordance with the TFT manufacturing steps in Embodiment mode 2,n-channel type TFTs were manufactured actually as an experiment andtheir electric characteristics were evaluated. Here, the results of theevaluation of the electric characteristics are described.

FIGS. 5A and 5B show data as to I_(D)-V_(G) (current-voltage)characteristics of the n-channel type TFTs that were obtained throughthe measurements carried out with respect to eight n-channel type TFTsusing a semiconductor measuring apparatus (4155B). FIG. 5A shows dataobtained in the case where the step of forming a chemical oxide filmmade of an ultrathin silicon oxide film was employed and FIG. 5B showsdata obtained in the case where the step of forming a chemical oxidefilm was omitted. Note that the channel length (L) and the channel width(W) of the n-channel type TFTs subjected to the measurement were 7.3 μmand 200 μm, respectively.

As can be seen from FIGS. 5A and 5B, the results were obtained thatvariations in I_(D)−V_(G) characteristics among the n-channel type TFTswere small when the chemical oxide film was formed, while variations inI_(D)−V_(G) characteristics among the n-channel type TFTs were greatwhen no chemical oxide film was formed. It is considered as the cause ofthe variations in I_(D)−V_(G) characteristics that the amorphous siliconfilm is etched with hydrogen ions during the channel doping and areduction in thickness of the amorphous silicon film progresses to causevariations in contact resistance.

From the above-mentioned results of the evaluation of the I_(D)−V_(G)characteristics, it has been proved that the chemical oxide film made ofan ultrathin silicon oxide film has completely no problem in serving asa protective film for channel doping.

As described above, a TFT having excellent electric characteristics canbe manufactured through application of the channel doping pretreatmentstep of forming a chemical oxide film and channel doping with respect tothe amorphous silicon film.

Embodiments Embodiment 1

The present embodiment is an example in which a channel dopingpretreatment step of forming a chemical oxide film on an amorphoussilicon film is applied to a step of manufacturing an active matrix typeliquid crystal display and is described concretely with reference toFIGS. 6A to 10B. The description with respect to the step ofcrystallizing an amorphous silicon film after channel doping is directedto the case of crystallization using a catalytic element.

First, a silicon oxynitride film 302 a with a thickness of 50 nm as thefirst layer and a silicon oxynitride film 302 b with a thickness of 100nm as the second layer that are different in composition ratio from eachother are deposited on a glass substrate 301 by the plasma CVD method toform a base film 302. Examples of the glass substrate 301 used hereininclude quartz glass, barium borosilicate glass, aluminoborosilicateglass, and the like. Next, an amorphous silicon film 303 a with athickness of 55 nm is deposited on the base film 302 (302 a and 302 b)by the plasma CVD method. In depositing the amorphous silicon film 303a, an ultrathin natural oxide film (not shown) is attached to thesurface of the amorphous silicon film 303 a due to the effect of oxygenin the air mixed into the treating atmosphere. Note that in the presentembodiment, the amorphous silicon film 303 a is deposited by the plasmaCVD method but may be formed by the low pressure CVD method (see FIG.6A).

During the deposition of the amorphous silicon film 303 a, there is apossibility that carbon, oxygen, and nitrogen present in the air may bemixed into the treating atmosphere. It has been known empirically thatcontamination by such impurity gases causes deterioration incharacteristics of TFTs eventually obtained. In view of this, thepresent inventors et al. have recognized that the contamination by theimpurity gases acts as a factor of crystallization inhibition. Hence, itis preferable to completely inhibit the impurity gases from being mixedinto the treating atmosphere. Specifically, it is preferable to set theimpurity gas concentration to be in the range of 5×10¹⁷ atoms/cm³ orless in both the cases of carbon and nitride and to be in the range of1×10¹⁸ atoms/cm³ or less in the case of oxygen (see FIG. 6A).

Next, the natural oxide film (not shown) attached to the surface of theamorphous silicon film 303 a is washed with dilute hydrofluoric acid,thereby cleaning the surface of the amorphous silicon film 303 a.Afterward, as a pretreatment for channel doping, an ozone watertreatment is carried out for a predetermined time to form a chemicaloxide film 304 made of an ultrathin silicon oxide film with a thicknessof 5 nm or less on the surface of the amorphous silicon film 303 a. Inthe present embodiment, the chemical oxide film 304 is formed by theozone water treatment but may be formed by a treatment with a hydrogenperoxide solution. Alternatively, an ultrathin silicon oxide film havinga similar effect to that of the chemical oxide film can be formed byultraviolet (UV) irradiation in an atmosphere containing oxygen althoughit is not an exact chemical oxide film (FIG. 6A).

When the hydrogen ion ratio is low in an ion doping apparatus used inthe channel doping step, it is also considered as the pretreatment forchannel doping that unsaturated bonds present at the amorphous siliconfilm 303 a surface are made to terminate with an element to be bondedwith bonding energy higher than that (71.5 kcal/mol) of Si—H bonds suchas oxygen.

Next, a resist pattern including resist pattern portions 305 to 308 toserve as a mask for channel doping is formed with using as its openingregions the regions corresponding to n-channel type TFTs 401 and 403 anda pixel TFT 404 of the amorphous silicon film 303 a. Afterward, usingthe ion doping apparatus, doping with a boron element as a p-typeimpurity is carried out with the resist pattern portions 305 to 308 usedas a mask, and thus channel doping is implemented as a first ion dopingprocess. In the channel doping, an ion source is used that is obtainedthrough dilution of diborane (B₂H₆) gas with hydrogen. Generally, thechannel doping is carried out under the doping conditions including adiborane dilution ratio of 0.01 to 1.0%, an accelerating voltage of 1 to50 kV, an ion current of 10 to 500 nA, and a dose of 1×10¹¹ to 1×10¹⁴atoms/cm². In the present embodiment, the doping process was carried outunder the channel doping conditions including a diborane dilution ratioof 0.1%, an accelerating voltage of 15 kV, an ion current of 50 nA, anda dose of 4×10¹³ atoms/cm² (see FIG. 6A).

Next, the resist pattern portions 305 to 308 that have served as a maskfor channel doping are removed. Afterward, washing is carried out by atreatment using dilute hydrofluoric acid to clean the surface of theamorphous silicon film 303 a. Afterward, an ozone water treatment iscarried out for a predetermined time to form a chemical oxide film (notshown) made of an ultrathin silicon oxide film on the surface of theamorphous silicon film 303 a. This chemical oxide film (not shown) isformed for the purpose of improving wettability with respect to a Niaqueous solution as a catalytic element solution to be applied later bya spin coating method. In the present example, the chemical oxide film(not shown) is formed by the ozone water treatment but may be formed bya treatment using a hydrogen peroxide solution (see FIG. 6B).

Next, a Ni aqueous solution as a catalytic element solution having aneffect of accelerating crystallization is applied to the whole surfaceof the amorphous silicon film 303 a. Specifically, nickel acetate as aNi compound is dissolved in pure water and then a Ni aqueous solutionwhose concentration has been controlled to be 10 ppm by weight isapplied by a spin process (see FIG. 6B).

Next, in order to control the amount of hydrogen contained in theamorphous silicon film 303 a to 5 atom % or less, the substrate isheat-treated in a nitrogen atmosphere inside an electrothermal furnaceat 450 C for one hour, thereby implementing dehydrogenation to removethe hydrogen contained in the amorphous silicon film 303 a (see FIG.6B).

Next, a heat treatment is carried out in the electrothermal furnace at550 C for four hours to crystallize the amorphous silicon film 303 a andthus a crystalline silicon film 303 b is formed. Afterward, in order toimprove the crystallinity of the crystalline silicon film 303 b thusobtained, laser irradiation is carried out with respect to thecrystalline silicon film 303 b. By this laser irradiation, thecrystallinity of the crystalline silicon film 303 b is improvedconsiderably. In the present embodiment, a pulse oscillation type KrFexcimer laser (with a wavelength of 248 nm) is applied. This excimerlaser has not only an effect of improving the crystallinity of thecrystalline silicon film 303 b but also an effect of improving theefficiency of gettering by a gettering source since the Ni element isbrought into a state where the Ni element can move very easily (see FIG.6B).

Next, pattern formation of the crystalline silicon film 303 b isconducted by the ordinary photolithography and dry etching to formsemiconductor films 309 to 313 to be channel, source, and drain regionsof TFTs (see FIG. 7A).

Next, a gate insulating film 314 made of a silicon oxynitride film witha thickness of 100 nm is deposited by the plasma CVD method to cover thesemiconductor films 309 to 313. In depositing the gate insulating film314, washing is carried out by a treatment with dilute hydrofluoric acidto clean the surfaces of the semiconductor films 309 to 313. Afterward,a conductive film as a gate electrode material is deposited on the gateinsulating film 314 by the sputtering method or the CVD method. As thegate electrode material used here, a heat resistant material ispreferable that can withstand the heat treatment temperature (about 550to 650 C) for gettering as a later step that also serves for activatingthe impurity elements. Examples of the heat resistant material includehigh melting metals such as Ta(tantalum), Mo(molybdenum), Ti(titanium),W(tungsten), Cr(chromium), and the like, metal silicide as a compound ofa high melting metal and silicon, polycrystalline silicon having n-typeor p-type conductivity, and the like. Note that in the presentembodiment, a gate electrode film 315 formed from a W film with athickness of 400 nm is deposited by the sputtering method (see FIG. 7B).

Above the substrate with the configuration described above are formedgate electrodes 322 to 325, an electrode 326 for storage capacitance,and an electrode 327 to function as a source wiring through theimplementation of photolithography and dry etching for the formation ofgate electrodes. After the dry etching, resist patterns 316 to 319 as amask for the dry etching remain on the gate electrodes 322 to 325.Similarly, resist patterns 320 and 321 remain on the electrode 326 forstorage capacitance and the electrode 327 to function as a sourcewiring, respectively. Note that the dry etching proceeds, the gateinsulating film 314 made of the silicon oxynitride film as a base isreduced in thickness to be deformed into a shape of a gate insulatingfilm 328 (see FIG. 8A).

Next, with the resist patterns 316 to 321 remaining, doping with a lowconcentration n-type impurity is carried out as a second ion dopingprocess using the ion doping apparatus with the gate electrodes 322 to325 and the electrode 326 for storage capacitance used as a mask. Theion doping process is carried out using a p element as an n-typeimpurity under the conditions including an accelerating voltage of 10 to100 kV and a dose of 3×10¹² to 3×10¹³ atoms/cm². By this second iondoping process, low concentration impurity regions (n⁻ regions) 334 to338 containing the n-type impurity are formed in the regions of thesemiconductor films 309 to 313 corresponding to the regions locatedoutside the respective gate electrodes 322 to 325 and the electrode 326for storage capacitance. At the same time, substantially intrinsicregions 329 to 332 to function as channels of the TFTs are formeddirectly under the gate electrodes 322 to 325. In the semiconductor film313 located directly under the electrode 326 for storage capacitance, anintrinsic region 333 to function as one of electrodes for capacitanceformation is formed since the region is not the TFT formation region butis a region where the storage capacitance 405 is to be formed (FIG. 8A).

Next, the substrate is washed with a special-purpose peeling liquid andthus the resist patterns 316 to 321 that have served as a mask for dryetching are removed. After the removal, in order to allow the n-channeltype TFTs 401 and 403 in a driving circuit 406 and the pixel TFT 404 ina pixel region 407 to have a lightly doped drain (LDD) structure, resistpatterns 339 to 341 for the formation of n⁺ regions to serve as a maskfor a third ion doping process are formed to cover the gate electrodes322, 324, and 325 that are present in the above-mentioned regions.Afterward, doping with a high-concentration n-type impurity is carriedout as the third ion doping process. The ion doping process is carriedout under the doping conditions including an accelerating voltage of 10to 100 kV and a dose of 1×10¹⁴ to 1×10¹⁶ atoms/cm². In the presentembodiment, the doping process was carried out under the conditionsincluding an accelerating voltage of 80 kV and a dose of 1.7×10¹⁵atoms/cm². By this ion doping process, high-concentration impurityregions (n⁺ regions) 342, 344, and 345 containing the n-type impurityare formed in the regions of the semiconductor films 309, 311, and 312corresponding to the regions located outside the resist patterns 339 to341. With the formation of the high-concentration impurity regions (n⁺regions) 342, 344, and 345, the low-concentration impurity regions (n⁻regions) 334, 336, and 337 that have already been formed are separatedinto the high-concentration impurity regions (n⁺ regions) 342, 344, and345 and the low-concentration impurity regions (n⁻ regions) 347 to 349and thus the source and drain regions to compose the LDD structure areformed (see FIG. 8B).

At this time, the region of the p-channel type TFT 402 of the drivingcircuit 406 and the region of the storage capacitance 405 in the pixelregion 407 that are regions other than the regions where the LDDstructures are formed are ion-doped with the gate electrode 323 and theelectrode 326 for storage capacitance used as a mask, respectively.Hence, high-concentration impurity regions (n⁺ regions) 343 containingthe n-type impurity are formed in the regions of the semiconductor film310 corresponding to the regions located outside the gate electrode 323,and high-concentration impurity regions (n⁺ regions) 346 containing then-type impurity are also formed in the regions of the semiconductor film313 corresponding to the regions located outside the electrode 326 forstorage capacitance (see FIG. 8B)

Next, by the ordinary photolithography, resist patterns 350 to 352 areformed with using as its opening regions the region of the semiconductorfilm 310 corresponding to the p-channel type TFT 402 and the region ofthe semiconductor film 313 corresponding to the storage capacitance 405.Afterward, with the resist patterns 350 to 352 used as a mask, dopingwith a high-concentration p-type impurity is carried out as a fourth iondoping process using the ion doping apparatus. By this ion dopingprocess, a boron element as a p-type impurity is ion-implanted into theregion of the semiconductor film 310 corresponding to the p-channel typeTFT 402 with the gate electrode 323 used as a mask. As a result,high-concentration impurity regions (p⁺ regions) 353 having p-typeconductivity are formed in the regions of the semiconductor film 310corresponding to the regions outside the gate electrode 323. Thehigh-concentration impurity regions (p⁺ regions) 353 have already beendoped with the phosphorous element as an n-type impurity but are dopedto contain a high concentration of boron element so that the dose of theboron element reaches 2.5×10¹⁵ atoms/cm². Thus, high-concentrationimpurity regions (p⁺ regions) 353 having p-type conductivity to functionas source and drain regions are formed. Similarly in the region wherethe storage capacitance 405 is formed, high-concentration impurityregions (p⁺ regions) 354 having p-type conductivity are also formed inthe regions of the semiconductor film 313 corresponding to the regionsoutside the electrode 326 for storage capacitance (see FIG. 9A).

Next, after the removal of the resist patterns 350 to 352, a firstinterlayer insulating film 355 made of a silicon oxynitride film with athickness of 150 nm is deposited by the plasma CVD method. Afterward,for the thermal activation of the impurity ions (the phosphorous andboron element) with which the semiconductor films 309 to 313 have beendoped, a heat treatment is carried out in an electrothermal furnace at600 C for 12 hours. This heat treatment is carried out for the thermalactivation of the impurity ions but also is intended to getter the Nielement present in the substantially intrinsic regions 329 to 332 tofunction as channel regions and the intrinsic region 333 to function asone of the electrodes for capacitance formation by the impurity ions.Note that the thermal activation may be carried out before thedeposition of the first interlayer insulating film 355. However, whenthe wiring materials for the gate electrodes or the like have low heatresistance, it is preferable to carry out the thermal activation afterthe deposition of the first interlayer insulating film 355. Afterward,in order to terminate unsaturated bonds present in the semiconductorfilms 309 to 313, a hydrogen treatment is carried out in a 3%hydrogen-containing nitrogen atmosphere at 410 C for one hour (see FIG.9B).

Next, a second interlayer insulating film 356 made of an acrylic resinfilm with a thickness of 1 .6 μm is formed on the first interlayerinsulating film 355. Afterward, contact holes are formed by the ordinaryphotolithography and dry etching so as to pass through the secondinterlayer insulating film 356, the first interlayer insulating film355, and the gate insulating film 328 as an underlayer film. At thistime, the contact holes are formed to be connected to the electrode 327to function as a source wiring and the high-concentration impurityregions 342, 344, 345, 353, and 354 (see FIG. 10A).

Next, conductive metal wirings 357 to 362 are formed to be electricallyconnected to the high-concentration impurity regions 342, 344, and 353of the driving circuit 406. Connection electrodes 363, 365, and 366 andgate wiring 364 in the pixel region 407 are formed with the sameconductive material. In the present embodiment, a laminated filmcomposed of a Ti film with a thickness of 50 nm and an Al—Ti alloy filmwith a thickness of 500 nm is applied as a constituent material for themetal wirings 357 to 362, the connection electrodes 363, 365, and 366,and the gate wiring 364. The connection electrode 363 is formed so as toelectrically connect the impurity region 345 with the electrode 327 tofunction as a source wiring. The connection electrode 365 is formed tobe electrically connected to the impurity region 345 of the pixel TFT404. The connection electrode 366 is formed to be electrically connectedto the impurity region 354 of the storage capacitance 405. In addition,the gate wiring 364 is formed to electrically connect a plurality ofgate electrodes 325 of the pixel TFT 404 to each other. Afterward, atransparent conductive film such as an indium tin oxide (ITO) film witha thickness of 80 to 120 nm is deposited and then a pixel electrode 367is formed by photolithography and etching. The pixel electrode 367 iselectrically connected to the impurity regions 345 as the source anddrain regions of the pixel TFT 404 through the connection electrode 365and is also electrically connected to the impurity region 354 of thestorage capacitance 405 through the connection electrode 366 (FIG. 10B).

As described above, a channel doping pretreatment step of forming achemical oxide film can be applied to the process of manufacturing anactive matrix type liquid crystal display having n-channel type TFTswith the LDD structure and a p-channel type TFT with a single drainstructure. Note that the application of the chemical oxide film to thechannel doping pretreatment step is advantageous of an improvement inprocessing capability in the channel doping step and a reduction inproduction cost.

Embodiment 2

The present invention relates to a method of manufacturing asemiconductor device having a circuit structure with TFTs. The presentinvention can be applied to the manufacture of various active matrixtype semiconductor displays, for example, a liquid crystal display andan EL display. Hence, the present invention can be applied to themanufacture of electronic equipment used in various fields having anactive matrix type semiconductor display (a liquid crystal display or anEL display) installed therein. Here, concrete examples of suchelectronic equipment are described with reference to FIGS. 11A to 13C.Examples of such electronic equipment include a video camera, a digitalcamera, a projector (of a rear type or a front type), a head mounteddisplay (a goggles-type display), game equipment, a car navigationsystem, a personal computer, a portable information terminal (a mobilecomputer, a portable telephone, an electronic book, or the like), andthe like.

FIG. 11A shows a personal computer including a body 1001, an image inputunit 1002, a display device 1003, and a keyboard 1004. The presentinvention can be applied to the display device 1003 and other circuits.

FIG. 11B shows a video camera including a body 1101, a display device1102, a voice input unit 1103, operation switches 1104, a battery 1105,and an image receiving unit 1106. The present invention can be appliedto the display device 1102 and other circuits.

FIG. 11C shows a mobile computer including a body 1201, a camera unit1202 provided with an image receiving unit 1203 and an operation switch1204, and a display device 1205. The present invention can be applied tothe display device 1205 and other circuits.

FIG. 11D shows a goggles-type display device including a body 1301,display devices 1302, and arm units 1303. The present invention can beapplied to the display devices 1302 and other circuits.

FIG. 11E shows a player for a recording medium containing programsrecorded therein (hereinafter simply referred to as a “recordingmedium”) that includes a body 1401, a display device 1402, speaker units1403, a recording medium 1404, and operation switches 1405. In thisdevice, a DVD, a CD, or the like is used as the recording medium. Thisdevice can be used for listening music, playing games, or internet. Thepresent invention can be applied to the display device 1402 and othercircuits.

FIG. 11F shows a portable telephone including a display panel 1501, anoperation panel 1502, a joint unit 1503, a display unit 1504, a voiceoutput unit 1505, operation keys 1506, a power switch 1507, a voiceinput unit 1508, and an antenna 1509. The display panel 1501 and theoperation panel 1502 are joined with the joint unit 1503. The angle ébetween the plane in which the display unit 1504 of the display panel1501 is disposed and the plane in which the operation keys 1506 of thecontrol panel 1502 are arranged can be changed arbitrarily by the jointunit 1503. The present invention can be applied to the display unit1504.

FIG. 12A shows a front type projector including a light source opticalsystem and display device 1601 and a screen 1602. The present inventioncan be applied to the display device 1601 and other circuits.

FIG. 12B shows a rear type projector including a body 1701, a lightsource optical system and display device 1702, mirrors 1703 and 1704,and a screen 1705. The present invention can be applied to the displaydevice 1702 and other circuits.

Note that FIG. 12C is a diagram showing an example of the configurationof the light source optical system and display device 1601 shown in FIG.12A and the light source optical system and display device 1702 shown inFIG. 12B. The light source optical systems and display devices 1601 and1702 each include a light source optical system 1801, mirrors 1802 and1804 to 1806, dichroic mirrors 1803, an optical system 1807, displaydevices 1808, phase difference plates 1809, and a projection opticalsystem 1810. The projection optical system 1810 has a configurationincluding a plurality of optical lenses with a projection lens. Thisconfiguration is called a three-plate type since three display devices1808 are used therein. In the optical path indicated with arrows shownin FIG. 12C, an operator may suitably provide an optical lens and a filmhaving a polarization function, a film for phase difference adjustment,an IR film, or the like.

FIG. 12D is a diagram showing an example of the configuration of thelight source optical system 1801 shown in FIG. 12C. In the presentembodiment, the light source optical system 1801 includes a reflector1811, a light source 1812, lens arrays 1813 and 1814, a lightpolarizing/transforming device 1815, and a condenser lens 1816. Notethat the light source optical system shown in FIG. 12D is an example andthe configuration of the light source optical system is not limited tothis. For instance, an operator may suitably provide the light sourceoptical system with an optical lens and a film having a polarizationfunction, a film for adjusting phase difference, an IR film, or thelike.

FIG. 13A shows an example of a single-plate type. The light sourceoptical system and display device shown in FIG. 13A include a lightsource optical system 1901, a display device 1902, a projection opticalsystem 1903, and a phase difference plate 1904. The projection opticalsystem 1903 includes a plurality of optical lenses with a projectionlens. The light source optical system and display device shown in FIG.13A can be applied to the light source optical systems and displaydevices 1601 and 1702 shown in FIGS. 12A and 12B. The light sourceoptical system shown in FIG. 12D may be used as the light source opticalsystem 1901. In addition, the display device 1902 is provided with acolor filter (not shown), thereby coloring display images.

A light source optical system and display device shown in FIG. 13B is anapplication example of FIG. 13A and display images are colored using anRGB rotary color filter disc 1905 instead of being provided with a colorfilter. The light source optical system and display device shown in FIG.13B can be applied to the light source optical systems and displaydevices 1601 and 1702 shown in FIGS. 12A and 12B, respectively.

A light source optical system and display device shown in FIG. 13C iscalled a color-filterless single-plate type. In this system, a displaydevice 1916 is provided with a microlens array 1915, and display imagesare colored using a dichroic mirror (green) 1912, a dichroic mirror(red) 1913, and a dichroic mirror (blue) 1914. A projection opticalsystem 1917 includes a plurality of optical lenses with a projectionlens. The light source optical system and display device shown in FIG.13C can be applied to the light source optical systems and displaydevices 1601 and 1702 shown in FIGS. 12A and 12B, respectively. Anoptical system with a coupling lens and a collimator lens in addition tothe light source may be used as a light source optical system 1911.

As described above, the method of manufacturing a semiconductor deviceof the present invention finds a very wide range of application. Thepresent invention can be applied to electronic equipment used in varietyof fields with an active matrix type liquid crystal display device andan EL display device installed therein.

The present invention relates to a method of manufacturing asemiconductor device having a circuit structure with TFTs and morespecifically to a pretreatment for doping a silicon-based semiconductorfilm such as a TFT active layer with impurity ions. The presentinvention has the following effects.

Effect 1

The present invention employs a simple pretreatment step of forming achemical oxide film or the like as a pretreatment in an ion doping stepand thus is effective in improving the throughput of the whole iondoping step.

Effect 2

Since an expensive plasma CVD apparatus or low pressure CVD apparatus isno longer necessary for the pretreatment in the ion doping step, thepresent invention is effective in reducing production cost.

The invention may be embodied in other forms without departing from thespirit or essential characteristics thereof. The embodiment modesdisclosed in this application are to be considered in all respects asillustrative and not limiting. The scope of the invention is indicatedby the appended claims rather than by the foregoing description, and allchanges which come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

TABLE 1 Experimental conditions of channel doping with respect to thesilicon-cotaining amorphous semiconductor film substrate No. chemicaloxide film diborane dilution ratio 1 None 0.1% B2H6/H2 2 Exist 0.1%B2H6/H2 3 None 1.0% B2H6/H2 4 Exist 1.0% B2H6/H2

1. A method of manufacturing a semiconductor device comprising: formingan amorphous semiconductor film comprising silicon over an insulatingsubstrate; forming a chemical oxide film on a surface of the amorphoussemiconductor film comprising silicon by using a liquid chemical; dopingthe amorphous semiconductor film comprising silicon with impurity ions;crystallizing the amorphous semiconductor film comprising; and formingat least one channel region comprising a portion of the dopedsemiconductor film.
 2. A method of manufacturing a semiconductor deviceaccording to claim 1, further comprising: washing a surface of theamorphous silicon film comprising silicon by using dilute hydrofluoricacid after forming the amorphous semiconductor film comprising siliconover the insulating substrate.
 3. A method of manufacturing asemiconductor device according to claim 1, wherein the chemical oxidefilm is formed by a treatment with ozone water.
 4. A method ofmanufacturing a semiconductor device according to claim 1, wherein thechemical oxide film is formed by a treatment with hydrogen peroxidesolution.
 5. A method of manufacturing a semiconductor device accordingto claim 1, wherein the chemical oxide film is 5 nm thick or less.
 6. Amethod of manufacturing a semiconductor device according to claim 1,wherein a material including hydrogen is used as an ion source for theimpurity ions used in the doping step.
 7. A method of manufacturing asemiconductor device according to claim 1, wherein a heat treatment isconducted to crystallize the amorphous semiconductor film comprisingsilicon.
 8. A method of manufacturing a semiconductor device accordingto claim 1, wherein a catalytic element having an effect of acceleratingcrystallization is applied to the amorphous semiconductor filmcomprising silicon, and a heat treatment is conducted to crystallize theamorphous semiconductor film comprising silicon.
 9. A method ofmanufacturing a semiconductor device according to claim 1, wherein thesemiconductor device is at least one device selected from the groupconsisting of a personal computer, a video camera, a mobile computer, agoggle type display device, a DVD player, a CD player, a portabletelephone, a front type projector and a rear type projector.
 10. Amethod of manufacturing a semiconductor device comprising: forming anamorphous semiconductor film comprising silicon over an insulatingsubstrate; terminating dangling bonds on a surface of the amorphoussemiconductor film comprising silicon with oxygen; doping the amorphoussemiconductor film comprising silicon with impurity ions; crystallizingthe amorphous semiconductor film comprising; and forming at least onechannel region comprising a portion of the doped semiconductor film. 11.A method of manufacturing a semiconductor device according to claim 10,further comprising: washing a surface of the amorphous silicon filmcomprising silicon by using dilute hydrofluoric acid after forming theamorphous semiconductor film comprising silicon over the insulatingsubstrate.
 12. A method of manufacturing a semiconductor deviceaccording to claim 10, wherein a material including hydrogen is used asan ion source for the impurity ions used in the doping step.
 13. Amethod of manufacturing a semiconductor device according to claim 10,wherein a heat -treatment is conducted to crystallize the amorphoussemiconductor film comprising silicon.
 14. A method of manufacturing asemiconductor device according to claim 10, wherein a catalytic elementhaving an effect of accelerating crystallization is applied to theamorphous semiconductor film comprising silicon, and a heat treatment isconducted to crystallize the amorphous semiconductor film comprisingsilicon.
 15. A method of manufacturing a semiconductor device accordingto claim 10, wherein the semiconductor device is at least one deviceselected from the group consisting of a personal computer, a videocamera, a mobile computer, a goggle type display device, a DVD player, aCD player, a portable telephone, a front type projector and a rear typeprojector.
 16. A method of manufacturing a semiconductor devicecomprising: forming an amorphous semiconductor film comprising siliconover an insulating substrate; terminating dangling bonds on a surface ofthe amorphous semiconductor film comprising silicon with an element tobe bonded with bonding energy higher than that of Si—H bonds; doping theamorphous semiconductor film comprising silicon with impurity ions;crystallizing the amorphous semiconductor film comprising; and formingat least one channel region comprising a portion of the dopedsemiconductor film.
 17. A method of manufacturing a semiconductor deviceaccording to claim 16, further comprising: washing a surface of theamorphous silicon film comprising silicon by using dilute hydrofluoricacid after forming the amorphous semiconductor film comprising siliconover the insulating substrate.
 18. A method of manufacturing asemiconductor device according to claim 16, wherein a material includinghydrogen is used as an ion source for the impurity ions used in thedoping step.
 19. A method of manufacturing a semiconductor deviceaccording to claim 16, wherein a heat treatment is conducted tocrystallize the amorphous semiconductor film comprising silicon.
 20. Amethod of manufacturing a semiconductor device according to claim 16,wherein a catalytic element having an effect of acceleratingcrystallization is applied to the amorphous semiconductor filmcomprising silicon, and a heat treatment is conducted to crystallize theamorphous semiconductor film comprising silicon.
 21. A method ofmanufacturing a semiconductor device according to claim 16, wherein thesemiconductor device is at least one device selected from the groupconsisting of a personal computer, a video camera, a mobile computer, agoggle type display device, a DVD player, a CD player, a portabletelephone, a front type projector and a rear type projector.
 22. Amethod of manufacturing a semiconductor device comprising: forming anamorphous semiconductor film comprising silicon over an insulatingsubstrate; forming a chemical oxide film on a surface of the amorphoussemiconductor film comprising silicon by using a liquid chemical; dopingthe amorphous semiconductor film comprising silicon with impurity ions;crystallizing the amorphous semiconductor film comprising silicon;patterning the crystallized semiconductor film comprising silicon toform at least one active layer; forming a gate insulating film over theactive layer; forming a gate electrode over the active layer with thegate insulating film interposed therebetween; and forming at least onechannel region comprising a portion of the doped semiconductor film. 23.A method of manufacturing a semiconductor device according to claim 22,further comprising: washing a surface of the amorphous silicon filmcomprising silicon by using dilute hydrofluoric acid after forming theamorphous semiconductor film comprising silicon over the insulatingsubstrate.
 24. A method of manufacturing a semiconductor deviceaccording to claim 22, wherein the chemical oxide film is formed by atreatment with ozone water.
 25. A method of manufacturing asemiconductor device according to claim 22, wherein the chemical oxidefilm is formed by a treatment with hydrogen peroxide solution.
 26. Amethod of manufacturing a semiconductor device according to claim 22,wherein the chemical oxide film is 5 nm thick or less.
 27. A method ofmanufacturing a semiconductor device according to claim 22, wherein amaterial including hydrogen is used as an ion source for the impurityions used in the doping step.
 28. A method of manufacturing asemiconductor device according to claim 22, wherein a heat treatment isconducted to crystallize the amorphous semiconductor film comprisingsilicon.
 29. A method of manufacturing a semiconductor device accordingto claim 22, wherein a catalytic element having an effect ofaccelerating crystallization is applied to the amorphous semiconductorfilm comprising silicon, and a heat treatment is conducted tocrystallize the amorphous semiconductor film comprising silicon.
 30. Amethod of manufacturing a semiconductor device according to claim 22,wherein the semiconductor device is at least one device selected fromthe group consisting of a personal computer, a video camera, a mobilecomputer, a goggle type display device, a DVD player, a CD player, aportable telephone, a front type projector and a rear type projector.31. A method of manufacturing a semiconductor device comprising: formingan amorphous semiconductor film comprising silicon over an insulatingsubstrate; terminating dangling bonds on a surface of the amorphoussemiconductor film comprising silicon with oxygen; doping the amorphoussemiconductor film comprising silicon with impurity ions; crystallizingthe amorphous semiconductor film comprising silicon; patterning thecrystallized semiconductor film comprising silicon to form at least oneactive layer; forming a gate insulating film over the active layer;forming a gate electrode over the active layer with the gate insulatingfilm interposed therebetween; and forming at least one channel regioncomprising a portion of the doped semiconductor film.
 32. A method ofmanufacturing a semiconductor device according to claim 31, furthercomprising: washing a surface of the amorphous silicon film comprisingsilicon by using dilute hydrofluoric acid after forming the amorphoussemiconductor film comprising silicon over the insulating substrate. 33.A method of manufacturing a semiconductor device according to claim 31,wherein a material including hydrogen is used as an ion source for theimpurity ions used in the doping step.
 34. A method of manufacturing asemiconductor device according to claim 31, wherein a heat treatment isconducted to crystallize the amorphous semiconductor film comprisingsilicon.
 35. A method of manufacturing a semiconductor device accordingto claim 31, wherein a catalytic element having an effect ofaccelerating crystallization is applied to the amorphous semiconductorfilm comprising silicon, and a heat treatment is conducted tocrystallize the amorphous semiconductor film comprising silicon.
 36. Amethod of manufacturing a semiconductor device according to claim 31,wherein the semiconductor device is at least one device selected fromthe group consisting of a personal computer, a video camera, a mobilecomputer, a goggle type display device, a DVD player, a CD player, aportable telephone, a front type projector and a rear type projector.37. A method of manufacturing a semiconductor device comprising: formingan amorphous semiconductor film comprising silicon over an insulatingsubstrate; terminating dangling bonds on a surface of the amorphoussemiconductor film comprising silicon with an element to be bonded withbonding energy higher than that of Si—H bonds; doping the amorphoussemiconductor film comprising silicon with impurity ions; crystallizingthe amorphous semiconductor film comprising silicon; patterning thecrystallized semiconductor film comprising silicon to form at least oneactive layer; forming a gate insulating film over the active layer;forming a gate electrode over the active layer with the gate insulatingfilm interposed therebetween; and forming at least one channel regioncomprising a portion of the doped semiconductor film.
 38. A method ofmanufacturing a semiconductor device according to claim 37, furthercomprising: washing a surface of the amorphous silicon film comprisingsilicon by using dilute hydrofluoric acid after forming the amorphoussemiconductor film comprising silicon over the insulating substrate. 39.A method of manufacturing a semiconductor device according to claim 37,wherein a material including hydrogen is used as an ion source for theimpurity ions used in the doping step.
 40. A method of manufacturing asemiconductor device according to claim 37, wherein a heat treatment isconducted to crystallize the amorphous semiconductor film comprisingsilicon.
 41. A method of manufacturing a semiconductor device accordingto claim 37, wherein a catalytic element having an effect ofaccelerating crystallization is applied to the amorphous semiconductorfilm comprising silicon, and a heat treatment is conducted tocrystallize the amorphous semiconductor film comprising silicon.
 42. Amethod of manufacturing a semiconductor device according to claim 37,wherein the semiconductor device is at least one device selected fromthe group consisting of a personal computer, a video camera, a mobilecomputer, a goggle type display device, a DVD player, a CD player, aportable telephone, a front type projector and a rear type projector.